title: Excitotoxic neuronal cell death during an oligodendrocyte-directed CD8+ T cell attack in the CNS gray matter.
abstract: BACKGROUND
  Neural-antigen reactive cytotoxic CD8+ T cells contribute to neuronal dysfunction and degeneration in a variety of inflammatory CNS disorders. Facing excess numbers of target cells, CNS-invading CD8+ T cells cause neuronal cell death either via confined release of cytotoxic effector molecules towards neurons, or via spillover of cytotoxic effector molecules from 'leaky' immunological synapses and non-confined release by CD8+ T cells themselves during serial and simultaneous killing of oligodendrocytes or astrocytes.
  
  
  METHODS
  Wild-type and T cell receptor transgenic CD8+ T cells were stimulated in vitro, their activation status was assessed by flow cytometry, and supernatant glutamate levels were determined using an enzymatic assay. Expression regulation of molecules involved in vesicular glutamate release was examined by quantitative real-time PCR, and mechanisms of non-vesicular glutamate release were studied by pharmacological blocking experiments. The impact of CD8+ T cell-mediated glutamate liberation on neuronal viability was studied in acute brain slice preparations.
  
  
  RESULTS
  Following T cell receptor stimulation, CD8+ T cells acquire the molecular repertoire for vesicular glutamate release: (i) they upregulate expression of glutaminase required to generate glutamate via deamination of glutamine and (ii) they upregulate expression of vesicular proton-ATPase and vesicular glutamate transporters required for filling of vesicles with glutamate. Subsequently, CD8+ T cells release glutamate in a strictly stimulus-dependent manner. Upon repetitive T cell receptor stimulation, CD25high CD8+ T effector cells exhibit higher estimated single cell glutamate release rates than CD25low CD8+ T memory cells. Moreover, glutamate liberation by oligodendrocyte-reactive CD25high CD8+ T effector cells is capable of eliciting collateral excitotoxic cell death of neurons (despite glutamate re-uptake by glia cells and neurons) in intact CNS gray matter.
  
  
  CONCLUSIONS
  Glutamate release may represent a crucial effector pathway of neural-antigen reactive CD8+ T cells, contributing to excitotoxicity in CNS inflammation.
authors.affiliation: Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, Münster 48149, Germany. nico.melzer@ukmuenster.de.
authors.forename: Nico
authors.initials: N
authors.lastname: Melzer
authors.forename: Gordon
authors.initials: G
authors.lastname: Hicking
authors.forename: Stefan
authors.initials: S
authors.lastname: Bittner
authors.forename: Nicole
authors.initials: N
authors.lastname: Bobak
authors.forename: Kerstin
authors.initials: K
authors.lastname: Göbel
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Herrmann
authors.forename: Heinz
authors.initials: H
authors.lastname: Wiendl
authors.forename: Sven G
authors.initials: SG
authors.lastname: Meuth
mesh_terms: D000818:Animals; D016923:Cell Death / Q000276:immunology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000473:pathology*; D009836:Oligodendroglia / Q000276:immunology*; D060888:Real-Time Polymerase Chain Reaction; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
chemical_list: D018698:Glutamic Acid